The prevalence of myopia is increasing globally. Complications of myopia are associated with huge economic and social costs. It is believed that high myopia in adulthood can be traced back to school age onset myopia. Therefore, it is crucial and urgent to implement effective measures of myopia control, which may include preventing myopia onset as well as retarding myopia progression in school age children. The mechanism of myopia is still poorly understood. There are some evidences to suggest excessive expansion of Bruch’s membrane, possibly in response to peripheral hyperopic defocus, and it may be one of the mechanisms leading to the uncontrolled axial elongation of the eyeball.
Myopia is the most common eye disorder worldwide, but it is often misinterpreted as merely a refractive error that can simply be corrected by spectacles, contact lenses, or refractive surgery. As a matter of fact, high myopia is often associated with an increased risk of a range of serious ocular complications, which may result in irreversible vision loss.
The World Health Organization (WHO) recently defined “high myopia” as −5 Diopter (D) or greater, which is associated with increased risk of blindness. Eyes with high myopia that develop degenerative changes in the macula, optic nerve and peripheral retina are considered as having pathologic myopia, and are at the highest risk of developing potentially blinding complications such as retinal detachments, myopic choroidal neovascularization (CNV), myopic macular degeneration, foveoschisis, glaucoma, and cataract.
Risk Factors and Causes
The projected increases in myopia are driven principally by lifestyle changes characterized by more near-work activities, like using computers and portable electronic devices, including smartphones. Other proposed risk factors for myopia include long hours spent in the classroom and less time outdoors, especially among young children.
People with progressive myopia are at higher risk of developing certain eye conditions that are associated with the elongation of the eye and stretching of the retina.
- Retinal detachment. A recent study revealed that people with progressive myopia have a 10 times greater risk of retinal detachment. This is because elongation of the eye causes stretching and thinning of the retina. This can result in rips in the peripheral retina and detachment of retinal tissue from the underlying layers of the interior of the eye.
- Glaucoma. Characterized by elevated pressure in the eye, glaucoma causes damage to the optic nerve and loss of peripheral vision. Symptoms include blurred vision, headaches, halos around lights and difficulty adapting to darkness.
- Cataracts. People with progressive and high myopia have a greater risk of cataracts than the general population. Also, cataracts tend to occur earlier in life among individuals with high myopia. Symptoms include blurred vision, halos around lights, glare, and reduced vibrancy of colors.
- Family history, lifestyle or both. It also tends to get worse as kids get older because their eyes continue to grow.
Kids spend a lot of time indoors at home and in classrooms, so whenever possible, try to plan more outdoor activities. Researchers further suggest that myopia progression may be caused by light levels, which can be directly related to how little time kids spend outdoors nowadays. According to the Vision Council, nearly one in four kids spend more than three hours per day using digital devices.
Increased outdoor activity has been shown to retard the onset of myopia by 11-34%.4 One possible reason for this is because components of sunlight activate vitamin D, which may play a potential role in eye growth. Also, kids are usually engaged in more distance-vision activities when they’re outside, which places fewer strenuous near-vision demands on young eyes.
Children’s eyes continue to grow, and as their myopia increases, the dependency on glasses increases. This can reduce the ability of children to participate actively in sports and other activities. Increasing myopia can also lead to eye health problems in the future.
Incidence and Prevalence
A recent review estimated that 22.9% of the world population has myopia. In the year 2000, 2.7% had high myopia, but by 2050, these figures will increase to 49.7%. In other words, almost 1 billion people will have high myopia suggesting an alarming increase of prevalence globally.
In a 2-year study amongst 87 children aged 7 and 13, it was found that Accommodative support spectacle lenses slowed down myopia progression by up to 62%.Strong evidence suggests that environmental factors play a crucial role in the development of school age onset myopia which include time spent outdoors , prolonged intense education, urbanization, near work, prenatal factors, and socioeconomic status. Outdoor activities and decreasing the duration of near work have been reported to be effective in delaying myopia onset.
Researchers at the Brien Holden Vision Institute in Sydney, Australia, found that an estimated 1.4 billion people worldwide were nearsighted in 2000. That's about 23 percent of the total global population. But by 2050, the researchers predict this figure will soar to 4.8 billion, afflicting 49.8 percent of the world's population.
The good news is, there are ways to protect your children from landing on the wrong side of this statistic. One key may be to encourage them to turn off their electronic devices and head outdoors.
Researchers and clinical practitioners continue to seek more-effective approaches to stop nearsightedness from getting worse over time.
Therapies that show the most promise to date include:
- Accommodative support spectacle lenses. These lenses worn daily for both far and near tasks help to correct myopia, besides controlling its evolution.
- Atropine:- Topical atropine drops are commonly used to dilate the pupil of the eye. However, research has shown that the myopia control effect from atropine does not continue after the first year of treatment, and that short-term use of atropine may not control nearsightedness significantly in the long run .Side effects which are loss of accommodation (the ability to see near objects clearly), and photophobia are the main cause of dropout during the trials.
- Increased time outside. Spending time outdoors during adolescence and your early adult years may decrease the lifetime risk of myopia.
- Orthokeratology. In this procedure, you wear rigid, gas permeable contact lenses while you sleep which changes the corneal curvature of your eye. If you discontinue this treatment, your eyes return to their former shape.
- Peripheral defocus modifying contact lenses. These Multifocal type contact lenses correct nearsightedness while keeping your eyes evenly focused on the periphery of your retina. Results from a two-year study revealed nearsighted children who wore multifocal soft contact lenses on a daily basis had 50 percent less progression of their myopia, compared with similarly nearsighted children who wore regular soft contact lenses.
- Early Myopia detection. The best way to take advantage of methods to control myopia is to detect nearsightedness early.Even if your child is not complaining of vision problems (nearsighted kids often are excellent students and have no visual complaints when reading), it's important to schedule routine eye exams for your children, starting before they enter preschool.
Early childhood eye exams are especially important if you or your spouse are nearsighted or your child's older siblings have myopia or other vision problems.
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- Considering myopia control | Optometry Times